In 1956 an excavaton at the site of Puruchuco, near Lima, revealed an urn which contained 21 khipu, most still in bundled form. This collection is the only group of khipu besides those from Chachapoyas with known provenance.
In the summer of 2004 Professor Urton re-studied the khipu in the Puruchuco Museum in Lima. The first examination of this group was completed in the late 1960’s by Carol Mackey. Dr. Mackey noted numeric matches between two khipu that were found rolled together, and further matching sequences between three separate khipu in this archive: UR064, UR068, and #9 (khipu #9 unfortunately could not be found in 2004, so it has not been examined by Dr. Urton. Its relationship to other khipu is presumed from data recorded by Dr. Mackey). Dr. Urton’s investigation confirmed these matches, and with the help of the database, additional relationships between the khipu were found.
The two khipu rolled together, UR066 and UR067, have almost identical string values, but on UR066 single and long knots are tied in the S direction, and on the other khipu they are tied Z. The color patterning is the same, but UR067 uses a grey-green in place of medium brown.
These two khipu, with 32 strings each, form the top level of a three-level heirarchy. The middle level contains three khipu: UR064, UR068, and #9. Each of these is divided into three groups; the cord-by-cord sums of these groups of pendants are equal to the cord values on UR067 ad UR066. The two khipu at the bottom tier have six groups of pendants; the cord-by-cord sums of these groups equal the values on the middle group of level 2. The dotted lines in the diagram represent the synthesis of information from one level to another.
Looking at UR068 in detail, it is clear that the three groups are each arranged into five groups of four with color seriation similar to UR066 and UR067. Summing the first cord of the first group, the first cord of the second group and the first cord of the third group gives the total value on the first cord of the summation group in UR067. This relationship holds for all of the cords on UR068.
The center group of UR068 holds a similar relationship to UR063. In this case there are six groups which, when summed together, result in numbers that match or are close to those in the center of UR068.